Plastic container

ABSTRACT

This invention relates to a container consisting of a thermoplastic material, with side walls, flat top and bottom panels of which the top panel is provided with at least one fill/drain opening, and with a continuous circumferential carrying and transport rim. For better utilization of pallet space, the container body has an approximately square cross-section with slightly convex lateral surfaces and slightly radiused corners. In order to counteract the inherent tendency of the flat container walls to bulge and buckle, the container body is provided with vertical and/or horizontal reinforcement elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of copending PCT International Patent application PCT/EP00/03643, filed Apr. 20, 2000, and a continuation-in-part of copending U.S. patent application Ser. No. 09/525,526, filed Mar. 15, 2000, the contents of both of which is expressly incorporated herein by reference thereto.

TECHNICAL FIELD OF INVENTION

[0002] The present invention relates to large-volume containers and, in particular, large-volume containers made from a thermoplastic material.

BACKGROUND OF THE INVENTION

[0003] Large-volume containers of the type discussed are typically in the form of a cylindrical drum having a capacity (volumetric net content) of about 16 to 80 gallons. These containers are commonly used for the storage and transportation of liquid contents or solid, particle-shaped and pasty contents.

[0004] A commonly employed container design is the bung-type drum with a net capacity of about 58 gallons. When these cylindrical drums or barrels are stored or shipped in ISO containers, there remains wasted space between the round wall surfaces of neighboring drums. Also, conventional drums of this type exhibit a tendency to buckle at their sides when multiple drums are stacked upon one another.

[0005] Therefore, it is desirable to provide a drum that avoids wasted space between adjacent drums, and at the same time does not tend to buckle when other drums are stacked upon it. The present invention provides such a drum.

SUMMARY OF THE INVENTION

[0006] According to the invention, this is accomplished by means of an approximately square cross-sectional shape of the drum body with slightly convex lateral surfaces and slightly radiused corners. Such a design results in a substantially improved utilization of pallet space. Compared to conventional, round drums, the essentially square drums according to this invention, when stacked side-by-side, leave significantly smaller gaps between them, thus permitting enhanced utilization of previously wasted carrier space (for instance in ISO containers). In a practical implementation of this invention, the lateral walls of the drum are provided with reinforcing vertical and/or horizontal ribs which will substantially reduce the tendency of the flat lateral wall panels to bulge or buckle. This buckling tendency increases as a function of the internal pressure, building up due to the hydrostatic pressure of the liquid contents, the weight of stacked drums, or the like. The reinforcing ribs may be in the form of molded-in U- or V-channels facing and protruding inward and/or outward.

[0007] In one embodiment of this invention, a sturdy drum body is obtained by means of continuous circumferential reinforcing elements in the form of enlarged annular wall protrusions. These reinforcing annular wall protrusions are preferably produced by an upset-stamping process during the blow molding of the drum body. In order for the upset-stamping-produced reinforcing rings to retain roughly the same outer diameter as the remaining drum wall, they are configured as a continuous, circumferential, fairly flat V-shaped outward-facing indentation.

[0008] In another preferred embodiment, the corners of the drum body are provided with deep angular indentations in such fashion that in the appropriate horizontal plane the drum has a nearly circular cross-section. This embodiment as well results in a considerable reduction of the buckling tendency especially in the lower half of the drum, thus permitting high stacking loads.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention is further explained and described below in the drawings of the embodiments that are presented. The following is shown:

[0010]FIG. 1 is a top view of a square drum-type container according to the present invention;

[0011]FIG. 2 is a side view of a square drum-type container according to the present invention, with the right side showing a partially cross-sectional representation of the upper and lower segments taken along line A-A of FIG. 1, and the left side showing a partially cross-sectional representation of a different embodiment according to the present invention;

[0012]FIG. 3 is a cross-section through the body of a square drum-type container according to the present invention, showing a circular footprint for comparison;

[0013]FIG. 4 is a side view of a modified drum according to this invention, with a partially cross-sectional representation of the upper and lower segments;

[0014]FIG. 5 is a top view of a preferred embodiment of the invention;

[0015]FIG. 6 is a side view of the container of FIG. 5, with a partially cross-sectional representation of the upper and lower segments;

[0016]FIG. 7 shows a diagonal cross-section of the drum of FIG. 5 taken along line B-B;

[0017]FIG. 8 illustrates the handling of a drum according to the present invention, lying sideways;

[0018]FIG. 9 illustrates the handling of a tipped drum according to the present invention; and

[0019]FIG. 10 is a top view of four palletized drums according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Reference number 10 shows a large-volume blow molded bung container made of thermoplastic material in FIG. 1 with a capacity of approximately 66 gallons, which is equipped on the upper wall of the container with a carrying and transport rim, or L-ring 12, that runs around the circumference of the container. L-ring 12 serves as a handling ring for lifting the drum with typical drum handling equipment. In the first end wall of the drum 10 are located two side bungs 14 in die-sunk, recessed bung wells 16. In this top view, the square cross-section becomes clear, namely that the drum bottom exhibits a sectional surface that approximates the shape of a square with side surfaces or side wall sections that are slightly embossed and rounded corner sections.

[0021]FIG. 2 shows an embodiment with a bung 14 centrally located in a bung well 16. In an alternate configuration, the drum 10 can have a larger, screw cap-equipped fill/drain opening with a larger diameter of, for instance, 6 inches or 10 inches. A screw cap-equipped drum 10 of that type is ideally suited as a reusable container for viscous, pasty or granular bulk material. According to one embodiment, the fill/drain opening may be centrally located on the top surface, or first end wall, of the drum 10. In the left half of the picture, the drum 10 is equipped with a reinforcing ring, or rolling ring 18, that runs around the circumference of the drum and allows it to be rolled over the floor, while in the right half of the picture, another embodiment without a rolling ring is shown.

[0022]FIG. 3 shows a cross-section through the wall of a drum body according to this invention, which drum can be designed with a loose lid. For comparison to the cross-section, a circle with the same circumferential length is superimposed over it. This circle is intended to show the usual bulging-out tendency of a drum filled with content. The internal pressure that builds up inside the drum 10 would cause the flat walls to bulge outwards while pulling in the corners, taking on the shape of the least structural stress, that being a circle. To work against this disadvantageous tendency, the drum body is provided with a continuous horizontal reinforcing element, as shown in FIG. 4.

[0023] To resist buckling of the side walls and to increase stackability, drum 10 is configured with at least one reinforcing element disposed about its circumference. In the left half of the illustration in FIG. 4, the reinforcing element is an annular protrusion 22 that runs around the drum's circumference. In the right half of the illustration, the reinforcing element is in the form of inward corner indentations 24. In either configuration, the reinforcing element (annular protrusion 22 or corner indentation 24) is measured at a height of about 43% from the drum 10 bottom, i.e., at the point where the square drum 10 is exposed to maximum buckling pressure. The annular protrusion 22 is configured as a shallow V-shaped, continuous indentation in such a fashion that the diameter of the annular protrusion 22 is roughly the same as that of the remaining drum body. Alternatively, the annular protrusion 22 can stick out slightly so that drums standing next to one another touch each other by way of the annular protrusion 22. In an alternate embodiment, drum 10 can be configured with any number of reinforcing elements disposed about its circumference.

[0024]FIG. 5 is a top view of the preferred embodiment of the drum 10. This embodiment of drum 10 has a first portion with a generally square cross-section, and a second portion with a generally round cross-section defined by four angular corner indentations 24 formed in the drum. The angular corner indentations 24 are outlined by the round dashed line, and are thickest in the corner areas and transition into the flat surfaces of the side wall sections in between.

[0025] In the preferred embodiment of FIG. 5, the second portion of the drum 10 has a nearly circular cross-section in the horizontal plane of maximum continuous indentation. Referring to the outline of the generally square drum 10, the ratio between the long radius 36, which is measured toward the corners, and the short radius 38, which is measured toward the midpoint of the side walls, is between 1.05 and 1.34 and preferably about 1.22.

[0026] As also shown in FIG. 5, drum 10 has on its top surface, or first end wall, two molded-in, mutually parallel reinforcing ribs 28. Reinforcing ribs 28 act to reinforce the upper surface of drum 10. In an alternate embodiment, any number of reinforcing ribs could be added to the top surface in varying orientations with respect to one another.

[0027]FIG. 6 shows the axial indentations 26 (axial reinforcing ribs) in the middle of the side wall sections of the square drum 10, serving to reinforce and stabilize the filled drum 10 against any buckling or bulging when subjected to stacked loads or internal pressures. In this particular embodiment, in contrast to a conventional square container such as a thin-walled canister, it is the flat side wall sections that support the axial load while the corner indentations 24 prevent any excessive radial bulging. The indentations 26 as well as reinforcing ribs 28 can be in the form of molded-in U- or V-shaped indentations or protrusions that face inward and/or outward.

[0028]FIG. 7 shows a diagonal cross-section of drum 10. In this case, the container with the angled indentations 24 and smaller corners has the largest overall cross-section. It is evident from this illustration how much more volumetric capacity (10%) is obtainable when compared to a cylindrical drum.

[0029]FIG. 8 shows a drum 10 according to this invention firmly lying in a sideways position 30. Without an external force, the drum 10 will not roll away in an uncontrolled fashion, yet the rounded corners allow it to be rolled and moved.

[0030]FIG. 9 shows how the drum 10, when tipped, can be rolled in its slanted position 32. In this slanted position even manual manipulation and rolling of the drum 10 using the rolling ring 18 is entirely possible without much of an effort.

[0031]FIG. 10 shows four square drums set on a standard-34 pallet (45 inches ×45 inches), with maximum utilization of the space between the drums. Thus, when drums according to this invention are stacked in an ISO container, for instance when shipped by truck, about 10% more bulk material can be shipped in the same space and at the same cost of transportation.

[0032] While it is apparent that the invention herein disclosed is well calculated to fulfill the objects above stated, it will be appreciated that numerous modifications and embodiments may be devised by those skilled in the art, and it is intended that the appended claims cover all such modifications and embodiments as fall within the true spirit and scope of the present invention. 

What is claimed is:
 1. A drum comprising: a side wall having end portions disposed at longitudinal ends thereof; first and second end walls located adjacent the end portions, the first end wall defining a fill/drain opening therein; a circumferential carrying and transport rim disposed on at least one of the end portions and configured for carrying the drum with drum handling equipment; and a first protrusion formed on the side wall configured and dimensioned to resist buckling of the side wall, wherein the drum defines a longitudinal axis between the end portions, and the protrusion extends substantially circumferentially about the side wall around the longitudinal axis.
 2. The drum of claim 1 , wherein the first protrusion extends inwardly toward the longitudinal axis.
 3. The drum of claim 2 , wherein the first protrusion defines an indentation on an exterior surface of the drum opposite to the protrusion.
 4. The drum of claim 1 , wherein the side wall comprises a plurality of side wall sections that define a substantially polygonal first cross-section of the side wall.
 5. The drum of claim 4 , wherein the side wall further comprises corner sections formed at intersections between the side wall sections, and the first protrusion cuts across the corner sections.
 6. The drum of claim 1 , wherein the drum defines a drum height between the end portions and substantially parallel to the longitudinal axis, and the first protrusion is disposed in a plane located at about 30% to about 70% of the drum height.
 7. The drum of claim 1 , wherein the side wall further comprises a second protrusion formed thereon, and the second protrusion extends substantially in a direction of the longitudinal axis.
 8. The drum of claim 1 , further comprising a reinforcing ring disposed adjacent one of the end portions, the reinforcing ring having at least one arcuate portion and being dimensioned to allow rolling of the drum about the reinforcing ring.
 9. The drum of claim 1 , further comprising at least one reinforcing rib formed in the end walls.
 10. A drum comprising: a side wall comprising: a first portion having a plurality of side wall sections that define a first circumferential cross-section, a second portion comprising angular indentations in the side wall disposed at intersections between the side wall sections defining a second circumferential cross-section that is different than the first cross-section and configured and dimensioned to resist buckling of the side wall, and end portions disposed at longitudinal ends of the side wall; first and second end walls located adjacent the end portions, the first end wall comprising a recessed well; and a fill/drain opening defined in the recessed well.
 11. The drum of claim 10 , wherein the second portion divides the first portion into upper and lower sections.
 12. The drum of claim 10 , wherein the drum defines a drum height between the end walls and substantially perpendicular to one of the end walls, and the second portion is located at about 30% to about 70% of the drum height.
 13. The drum of claim 10 , wherein the first cross-section is substantially polygonal.
 14. The drum of claim 10 , wherein the first cross-section is substantially square and the second cross-section is substantially annular.
 15. The drum of claim 10 , wherein the angular indentations are substantially V-shaped and are deepest at the intersections and transition into the side wall sections such that the second cross-section is substantially annular.
 16. The drum of claim 10 , wherein the V-shaped indentations are spaced apart a predetermined distance such that each V-shaped indentation does not transition into each adjacent V-shaped indentation.
 17. The drum of claim 10 , wherein the drum defines a drum height along the longitudinal axis and between the end portions, wherein the V-shaped indentations are disposed in a plane located at about 30% to about 70% of the drum height.
 18. The drum of claim 10 , further comprising a protrusion formed one of the walls for stiffening the at least one wall.
 19. A drum comprising: a side wall comprising a first portion having a plurality of side wall sections of substantially equal length that define a substantially polygonal first cross-section of the side walls, the side wall having end portions disposed at longitudinal ends thereof; first and second end walls located adjacent the end portions, the first end wall defining a fill/drain opening; and a circumferential carrying and transport rim disposed on at least one of the end portions and configured for carrying with drum handling equipment.
 20. The drum of claim 19 , wherein the first cross-section is substantially square.
 21. The drum of claim 19 , further comprising a protrusion formed on a surface of at least one of the walls for stiffening the at least one wall.
 22. The drum of claim 19 , wherein the protrusion protrudes inwardly into the drum.
 23. The drum of claim 19 , wherein the at least one wall comprises at least one of the side wall sections, and the protrusion extends substantially circumferentially.
 24. The drum of claim 19 , wherein: the drum defines a longitudinal axis between the end walls; the at least one wall comprises at least one of the side wall sections; and the protrusion extends substantially in a direction of the longitudinal axis.
 25. The drum of claim 19 , wherein the side wall has a substantially uniform thickness.
 26. The drum of claim 19 , wherein the first cross-section comprises four convex wall sections connected by four radiused corner sections, and a first radius is measured from a center of the first cross-section to a midpoint of the wall sections, and a second radius is measured from the center of the first cross-section to a midpoint of the corner sections, wherein the second radius is between about 10% and about 50% longer than the first radius.
 27. The drum of claim 19 , wherein the drum is of plastic material and has a volumetric capacity of between about 10 gallons and about 80 gallons, and at least one of the wall sections is reinforced such that the drum can support at least one second similar drum that is substantially filled and stacked on top of the drum for resisting buckling of the wall sections.
 28. The drum of claim 19 , wherein the circumferential carrying and transport rim comprises an outwardly protruding lip substantially having an L-shape and configured such that the drum can be lifted by the transport rim using drum handling equipment. 